1. Field of the Invention
The present invention relates to surgical knives, and more particularly to multiple bladed surgical knives with adjustable blades used in hair transplantation procedures.
2. Description of the Related Art
Many hair transplantation procedures have been developed which transfer hair and living hair follicles from a donor to a donee. For example, a circular punch is commonly used to form a small diameter hole in the scalp of a donee.
Thereafter, a skin graft containing hair and follicles which has been removed from a donor is transplanted to the hole left by the punch. The size of the hole left by the punch often controls the number of hairs which may be transplanted in a single graft; usually, only a small number of hairs, such as 2 to 6 hairs are transplanted in a single graft. Sometimes, even a single hair is transplanted. Thus, a typical hair transplantation procedure requires a large number of grafts, which must be obtained from a donor. In some instances, hair is removed from and transplanted to the same individual.
Initially, grafts were obtained by carefully cutting sections of hair-laden scalp using a scalpel, which was a tedious and difficult procedure. In order to simplify the removal of grafts, knives with multiple parallel blades were developed such as the knife 100 depicted in FIG. 1A. These known knives permit removal of long strips of hair-laden skin from a donor. As illustrated in FIG. 1A, known multiple bladed knives 100 have three or more parallel blades 101 enabling removal of more than one donor strip of skin in a single operation. The blades 101 of the known knife 100 each have openings which receive a pair of pins 103, 105. One of the pins 105 is typically threaded and receives a nut 106 which secures the blades 101 to a blade handle 107. When used to obtain skin strips from a donor's scalp, the knife 100 is positioned perpendicular to the donor's scalp, inserted to the desired depth and drawn along a number of centimeters, producing the above described strips of hair-laden skin. These strips are then cut into the numerous individual grafts typically required for hair transplantation to a donee.
Hair customarily grows at an angle with respect to the surface of the scalp. Likewise, the hair follicles located below the skin are also at an angle with respect to the surface of the scalp. When removing strips of hair-laden skin, the knife edges of a multiple bladed knife which is positioned perpendicular to the donor's scalp often inadvertently destroy hair follicles located below the scalp because they are located within the blades' path below the skin even though the hair itself may not be within the blades' path above the skin. In some instances, only 20% of the hair follicles on a donor strip remain intact for successful transplantations.
Thus, surgeons removing strips of skin with multiple bladed knives such as the knife 100 often orient the blades parallel to the direction of hair and follicle growth to minimize the chance that follicles may be destroyed. By angling the knife blades parallel with the direction of hair growth, less hair follicles are destroyed when the knife blades are drawn through the scalp tissue. This procedure permits a surgeon to cut a larger number of individual skin grafts from fewer donor strips.
However, angling the knife 100 of FIG. 1A in such a manner generally produces undesirable results because angulation naturally forces some blades to penetrate the scalp further than others. More specifically, if the knife 100 is angled such that a lower surface 109 of the handle 107 is nearest the scalp, the blades closest to the lower surface 109 will penetrate the scalp further than the blades farthest from the lower surface 109. Such angled blades could penetrate the scalp too deeply, risking damage to adjacent follicles, and may unnecessarily injure the donor by cutting into the donor's skull. Likewise, too shallow blade penetrations are insufficient to properly remove the hairs and follicles.
Thus, knives with multiple parallel and staggered blades were developed, such as that disclosed in International Publication Number WO 96/06566 by Arnold et al., which is illustrated in FIG. 1B. The knife 200 of FIG. 1B includes parallel and staggered blades 201. The blades 201 are held in place by two pins 203, 205, which are at an angle with respect to the handle 207, rather than extending perpendicular therefrom. This configuration staggers the blade tips at a single angle with respect to the longitudinal axis of a blade handle 207. The staggering of the blades 201 at a fixed angle permits the blades to be introduced to the scalp at a constant angle such that each donor strip is uniform in depth.
Because the blades 201 are solely held in place by the pins 203, 205, and secured by the nut 206, the blades are generally unstable, especially when subjected to lateral, twisting, and longitudinal forces experienced during operation. This instability complicates the donor strip removal procedure.
A surgeon using such a staggered blade knife 200 begins the strip removal procedure by evaluating the direction of hair growth at the position where the incisions are initially to be started. The surgeon then chooses a multiple bladed knife 200, such as the knife shown in FIG. 1B, which has the same angle as that of the hairs. Next, the surgeon orients the position of the knife 200 so that the blades 201 are aligned and parallel with the hairs. Thereafter, the blades 201 are pressed into the scalp while maintaining the parallel orientation of the blades with the hairs.
Typically, the direction of hair growth with respect to the scalp changes in different areas of the scalp of a single donor. Because of these changes, the surgeon must continually re-evaluate the orientation of the hairs growing in the scalp. As the direction of the hairs changes, the surgeon must readjust the orientation of the knife 200 relative to the hairs such that the blades 201 remain generally parallel to the hairs at all times during translation. This procedure must be done to prevent damage to a large number of follicles located within and outside the donor strip.
Regrettably, once the surgeon readjusts the orientation of the fixed angle knife 200 to prevent damage to follicles, the depth of the donor strip changes. Because the angle of the hair often changes dramatically throughout the scalp, a surgeon typically will select an area of the scalp for donor strip removal and then choose a knife with staggered blades approximating the average angle in the selected area.
However, the average orientation of the hair on the selected scalp area varies on different individual's heads and at different areas of the head. To properly address the average angle of the hair in a selected area, the surgeon must have a plurality of knives of numerous fixed blade angles to match the different average hair angles in order to maintain the uniform thickness of the donor strips and to prevent damage to the hair follicles—an extremely impractical solution to a reoccurring problem.
When using the knives 100, 200, the surgeon must continually approximate the depth that each of the blades should penetrate the scalp to achieve adequate depth penetration so that the entire follicle is removed while preventing contact with the skull. This depth approximation is difficult for surgeons inexperienced in donor strip removal operations. Because of the uncertainty associated with estimating the blade penetration depth, a surgeon may injure the donor by cutting too deeply into the scalp. Likewise, if the blades penetrate to deeply in an angular direction, the surgeon may unintentionally damage the follicles in the donor strip. Furthermore, the surgeon may insufficiently penetrate the surface of the scalp such that the hair follicles are not removed with the donor strip.
The previous described problems associated with current multiple bladed surgical knives limits their range of use. Human hair grows from the scalp in a variety of directions from one area of the scalp to another. Because of the above identified problems of current multiple bladed surgical knives, it is tedious and difficult to remove donor hair strips of constant depth without damaging a vast number of follicles in the donor strip. The previously described constraints of current multiple bladed surgical knives has created a need for a solution.